High Quality Content by WIKIPEDIA articles! A riot gun or less-lethal launcher is a type of firearm that is used to fire "non-lethal" ammunition for the purpose of suppressing riots. Less-lethal launchers may be special purpose firearms designed for riot control use, or standard firearms, usually shotguns and grenade launchers, adapted to riot control use with appropriate ammunition. Many of them are 37 mm or 40 mm caliber (about 1.5 inches).